The present invention relates to expendable decoys and, more particularly, to an advanced airborne expendable decoy system adapted to be towed behind military aircraft.
Aircraft decoys are used to draw various types of guided weapons away from an aircraft that the weapons are intended to destroy. Such systems contain various types of electronic circuits to create an apparent target to the weapon to attract the weapon to the decoy, rather than the aircraft.
Various types of thermal and electronic towed decoy devices have been used for many years as defensive systems for aircraft. Such devices include flares designed to attract infrared guided missiles and active electronic devices (e.g. transponders) adapted to receive radar signals and rebroadcast an amplified return signal. The flare or transponder is designed to present a larger thermal or electronic target than the aircraft from which it is deployed and thereby attract the weapon away from the aircraft. As the programming of anti-aircraft weaponry becomes more sophisticated to better discriminate between decoys and aircraft, the need to provide decoys with enhanced capabilities similarly evolves. Moreover, insofar as different anti-aircraft weapons utilize different types of electronic or thermal imaging systems, there exists a need to maintain an adequate inventory to defeat an attack by any of a variety of different types of anti-aircraft weapons that may be fired at the aircraft.
The principal limitations in the use of various types of thermal and electronic decoying devices are the space, weight, and economic limitations relative to the inclusion of any type of ordinance aboard an aircraft. Inclusion of a large number of expendable defensive systems may result in weight and drag penalties that may limit the performance envelope of the aircraft and thereby limit the pilot's ability to maneuver the aircraft away from a threat. Accordingly, it is highly desirable to devise towed decoys and towed decoy deployment systems that can cooperate with on-board defensive systems to defeat a variety of different types of anti-aircraft threats, with minimum space requirements and without imposing undue weight or drag penalties on the aircraft performance.
Aside from the aforementioned limitations relating to the aircraft performance, other limitations exist with respect to the maintenance of towed decoy deployment systems. One such limitation relates to the conventional use of pyrotechnic explosive charges to rapidly deploy, i.e. eject, the decoy from the aircraft as needed. Conventional towed decoy systems utilize decoys disposed in cannisters having explosive ejection charges contained within the body of the cannister between the towline spool or payout mechanism and the stored decoy. Because the explosive charges have a limited shelf life, cannisters which have exceeded that shelf life heretofor have been required to be disassembled to replace the explosive ejection charge. Due to system complexity, such disassembly is not normally permissible by aircraft maintenance technicians in the field and therefore must be performed at depot level maintenance facilities. Thus, the cannisters would typically be removed and shipped to remote maintenance facilities to affect periodic replacement of the ejection charge. Such procedures limit the readiness status of the equipment and contribute to unacceptable expenses which detract from efficient use of limited amounts of defense funds.
These above-referenced deficiencies have been addressed and alleviated by the invention disclosed in co-pending United States patent application Ser. No. 003,248, filed on Jan. 12, 1987, entitled TOWED DECOY SYSTEM now issued as U.S. Pat. No. 4,178,320, the disclosure of which is expressly incorporated herein by reference. Through the continued development of such towed decoy systems, further problematic deficiencies have been identified which detract from the overall effectiveness of towed decoy systems. Foremost has been the recognition that space limitations existing on military aircraft will require, in some instances, the deployment of the towed decoy system in an orientation or direction perpendicular to the airstream of the aircraft wherein friction arising from high aerodynamic side load upon the decoy entering the airstream may cause the decoy to be improperly deployed, or in severe instances become stalled within the decoy ejection cannister. As will be recognized, improper deployment in such instances will at least prohibit the proper operation of the decoy system and further may adversely affect the maneuverability of the aircraft.
In addition, deployment of towed decoys in an orientation perpendicular to the airstream of the aircraft typically imposes substantial increased strength requirements to the tow cable wherein conventional tow line payout and terminations are rendered ineffective causing the tow line to snap during deployment, rendering the towed decoy irretrievably lost.
Further, in view of pyrotechnic explosive charges additionally being utilized in such towed decoy systems for shearing or cutting the towline after deployment with such pyrotechnic explosive charges additionally having a finite shelf life, the prior art towed decoy systems utilizing differing pyrotechnic charges for ejection of the decoy from the aircraft and shearing of the towline serve to increase pyrotechnic charge inventories.
As such, there exists a substantial need in the art for an improved towed decoy system which is specifically adapted to permit rapid and fail-safe ejection and subsequent deployment of the decoy systems in both perpendicular and non-perpendicular orientations to the aircraft airstream, and further permits interchangeability of pyrotechnic charges between the ejection sub-assembly and towline cutter sub-assembly of the towed decoy system.